The wireless communication system is being extensively developed in order to provide diverse types of communication devices, such as voice or data services, and so on. Generally, a wireless communication system corresponds to a multiple access system that can support communication with multiple users by sharing an available system source (bandwidth, transmission power, and so on). Examples of the multiple access system may include a CDMA (code division multiple access) system, a FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, a SC-FDMA (single carrier frequency division multiple access) system, a MC-FDMA (multi carrier frequency division multiple access) system, and so on.
Device-to-Device (D2D) communication refers to a communication method that can directly send and receive voice, data, and so on, to and from user equipments without passing through a base station (evolved NodeB; eNB) by setting up a direct link between User Equipments (UEs). D2D communication may include methods, such as user equipment-to-user equipment (UE-to-UE) communication, Peer-to-Peer communication, and so on. Additionally, the D2D communication method may also be applied to M2M (Machine-to-Machine) communication, MTC (Machine Type Communication), and so on.
D2D communication is being considered as one of many solutions for resolving the load of the base station caused by the data traffic, which is increasing at a vast rate. For example, since data can be sent and received to and from user equipments without passing through the base station, unlike in a conventional (or legacy) wireless communication system, network overload may be reduced when using D2D communication.